HalfComplex.h

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#pragma once
 
namespace Mantid {
namespace CurveFitting {
 
class HalfComplex {
  size_t m_size;  
  double *m_data; 
  bool m_even;    
public:
  HalfComplex(double *data, const size_t &n) : m_size(n / 2 + 1), m_data(data), m_even(n / 2 * 2 == n) {}
  size_t size() const { return m_size; }
 
  double real(size_t i) const {
    if (i >= m_size)
      return 0.;
    if (i == 0)
      return m_data[0];
    return m_data[2 * i - 1];
  }
  double imag(size_t i) const {
    if (i >= m_size)
      return 0.;
    if (i == 0)
      return 0;
    if (m_even && i == m_size - 1)
      return 0;
    return m_data[2 * i];
  }
 
  void set(size_t i, const double &re, const double &im) {
    if (i >= m_size)
      return;
    if (i == 0) // this is purely real
    {
      m_data[0] = re;
    } else if (m_even && i == m_size - 1) // this is also purely real
    {
      m_data[2 * i - 1] = re;
    } else {
      m_data[2 * i - 1] = re;
      m_data[2 * i] = im;
    }
  }
};
 
} // namespace CurveFitting
} // namespace Mantid